1. Field
Example embodiments may provide a magnetic device, for example, a magnetic device that may write and/or read a plurality of bits of data using a magnetic domain dragging technique, and a method of operating the same.
2. Description of the Related Art
Magnetic devices for information storage may be classified into roughly two categories: memory devices and storage devices. Memory devices benefit from improved solid-state performance, while storage devices benefit from improved storage capacity.
A magnetic random access memory (MRAM) is a type of non-volatile memory device and a new solid-state magnetic memory that uses magnetic resistance generated from a spin-dependent conduction phenomena of nano-magnetic material. An MRAM may use giant magnetoresistance (GMR) or tunnel magnetoresistance (TMR) generated by an externally-applied magnetic field's effect on electron position and net spin. Spin may be considered as a degree of freedom of electrons.
GMR is a resistance difference generated when ferromagnetic layers having a non-magnetic material placed between them have the same magnetization directions and have reverse magnetization directions in an adjoining arrangement of ferromagnetic material/metallic non-magnetic material/ferromagnetic material. TMR is resistance where a current easily flows if two ferromagnetic materials have the same magnetization direction in an adjoining arrangement of ferromagnetic material/insulator/ferromagnetic material compared to when the two ferromagnetic materials have reverse magnetization directions. Because an MRAM using GMR may have a relatively small resistance difference caused by a magnetization direction, a large voltage difference may not be possible to achieve. Also, because MRAMs have a relatively large size of metal oxide semiconductor field effect transistor (MOSFET) combining with a GMR layer to constitute a cell, there is a strong need for MRAMs with a TMR layer.
The MRAM may include a transistor, which is a switching device, and/or a magnetic tunnel junction (MTJ) cell in which data is stored. The MTJ cell may include a pinned ferromagnetic layer having a pinned magnetization direction, a free ferromagnetic layer whose magnetization direction may be parallel to or anti-parallel to the pinned magnetization direction of the pinned ferromagnetic layer, and/or a non-magnetic layer between the pinned ferromagnetic layer and the free ferromagnetic layer that magnetically separates the pinned ferromagnetic layer and the free ferromagnetic layer.
Because a related art MRAM may store only one bit of data per MTJ cell, the data storage capacity of the MRAM may not be increased to desired levels. A new storage technology may be required to increase the information storage capacity of a related art magnetic memory such as the MRAM.